Method and system for synchronizing loads before injection on a tilt tray type sorting system

ABSTRACT

A method for synchronizing loads before the injection thereof on a sorting machine, consisting of trays which pass in front of an injection system comprising conveyors for moving the loads towards an injection site, a synchronization conveyor for positioning a load in order to place it on a tray, a device for injecting a load from the synchronization conveyor onto the machine and a cell for detecting the position of the loads at the exit of the synchronization conveyor. When a load passes the cell, the synchronization conveyor and the injection device are reversed and accelerated slightly to a top speed of V AR , so that the load returns to obscure the cell; the reverse movement is maintained until the cell is no longer obscured; and the synchronization conveyor is moved forward and accelerated slightly to a top speed of V AV  until the cell is obscured.

BACKGROUND OF THE INVENTION

The present invention relates to a method for synchronizing loads beforeinjection onto a sorting system, in particular a tilt tray type sortingmachine. It also relates to a system for the implementation of thismethod.

These machines are made up of a chain of carts moving around a track,generally in a loop, but which can also be in the form of a rail circuitwith semi-autonomous carts using DCV technology, at a predeterminednon-zero speed. Each cart is equipped with a tilt tray, which allows forthe load being carried to be discharged at a predetermined location,according to known processes.

The invention relates to the injection method, that is, the processallowing for a pre-determined tray to be loaded with a load such as aparcel or a piece of baggage.

Particularly with regard to baggage, the loads have a wide variety ofgeometrical shapes, materials and various appendages (straps, belts,retractable wheels, etc.) and are of variable masses, which makes theirgrip, and consequently their kinematic behaviour, practicallyunpredictable.

The invention describes a method for improving the reliability ofinjection, that is, the correct positioning of each load takenindividually on a sorting machine tray.

The arrows indicate the direction of movement of the loads.

FIG. 1A shows a top view of a set of trays 1AP moving at apre-determined speed in front of the injection device, which is made upof the following, in the order of movement of the loads:

-   -   two spacer type conveyors 1AQ1, 1AQ2 well known in the art,        which ensure the movement of the loads one by one towards the        actual injection device,    -   a synchronization conveyor 1AS, the function of which is to        place the load in a position allowing for it to be placed on a        tray in ballistic mode,    -   an injection device 1Al, generally made up of a set of drive        belts, which carries out such placement.

The loads are individually presented to the conveyor 1AS according toknown processes, which consist of positioning them one by one so thattheir front edge obscures the photoelectric cells 1AQ1C, 1AQ2C.

As soon as the conveyor 1AS is emptied of the previous load, theconveyor is started according to a pre-determined acceleration law γ1until the cell 1AS1 is obscured, and then according to a pre-determinedacceleration law γ2 until the cell 1AS2 is obscured.

At this stage, the controls simultaneously start the conveyor 1AS andthe injection device 1Al to give the load a speed, the component in thedirection of travel of the trays on the sorting machine of which isequal to the linear speed of the said trays.

As a point of information, injection at 45° relative to the sortingmachine means that this injection speed is of the order of √2× thelinear speed of the sorting machine. The means of stabilizing the loaddespite the transverse component are known. This only occurs when themotorized conveyors are driving the load without any notable sliding orrolling, as shown in FIG. 1B.

When the load does not have the required grip or is likely to roll onthe conveyors, the situation is as shown in FIG. 1C, where the load hasovershot the obscuring position for the cell 1AS2.

In the known state of the art, this situation, which means that thecorrect placing of the load on a tray on the sorting machine cannot beforeseen, can be detected.

In the known state of the art, the automatic controls trigger an alarm(for example a stop and a light signal) to request human intervention.

There are injection lines in the known state of the art known as dynamicinjection lines, designed in such a way that they only stop the loads ifthe sorting machine does not have sufficient empty trays to allow forthe load to continue moving.

However, if this is not the case, this type of injection line, whichlargely reproduces the risk related to the load sliding or rolling asalready described, also has a stand-by stop.

The management of such incidents presents a certain number of knowndisadvantages, particularly when the injection line is part of a baggagehandling and sorting system.

One of the requirements of such systems is the systematic inspection ofthe baggage for the detection of any suspicious contents such asexplosives.

Such detection takes place through the insertion of a specialistapparatus and intermediate conveyor means upstream of the injection linefor final sorting, as illustrated in the diagram in FIG. 1D.

This apparatus includes:

-   -   baggage identification means (1D1), for example the optical        reading of a bar code printed on a label when the baggage was        checked in,    -   means of detecting the possible presence of suspicious contents        (1D2), such as X-ray apparatus.

After identification, the intermediate conveyor devices and theinjection must use known methods to reliably monitor the position of thebaggage, in order to keep track of the identification and status,suspicious or not, of each checked piece of baggage.

For example, it is customary to use a sorting machine to send bothrisk-free baggage to its final destination (aircraft loading station)and baggage that presents a risk to stations for closer inspection.

The slippage of a piece of baggage on injection therefore creates asituation of uncertainty with regard to the location of one or evenseveral pieces of baggage.

In the known injection techniques, the detection of a slippage requireshuman intervention that consists of:

-   -   either removing the piece of baggage for manual handling,    -   or repositioning it so that it obscures the cell 1AS2 again,        which, as long as the control means permit, allows for the        normal process to continue with the loss of monitoring        considered to be corrected.

In any case, the said human intervention results in:

-   -   operating costs linked to the availability of sufficient        competent operators,    -   risks linked to human error with regard to security.

For example, some baggage sorting installations are manned to this endby as many operators as injections, thus considerably adding tooperating expenses.

In any case, each injection stoppage results in a loss of throughputthat prejudices the operational output of the system.

SUMMARY OF THE INVENTION

The aim of the present invention is to remedy these disadvantages byproposing an injection procedure that in most cases allows for thepositioning of the loads to be automatically corrected before injection,so that human intervention and the related costs are significantlyreduced.

This aim is achieved with a method for synchronizing loads before theirinjection onto a tilt tray type sorting machine, this machine having aset of trays moving at a pre-determined speed in front of an injectionsystem made up of conveyor means to move the loads one by one towards aninjection site, a so-called synchronization conveyor 1AS to place a loadcoming from the said conveyor means in a position allowing for it to beplaced on a tray in ballistic mode, a device 1Al to inject a load comingfrom the said synchronization conveyor onto the sorting machine, andmeans of detecting the position of the loads within the injection systemcomprising a detection cell arranged approximately at the exit of thesynchronization conveyor.

According to the invention, when a load has overshot the exit detectioncell, the following stages take place:

-   -   control of the synchronization conveyor 1AS and the injection        device 1Al according to a reversal with slight acceleration and        a top speed of a pre-determined value V_(AR), so that the load        returns to obscure the exit detection cell 1AS2,    -   continuation of the reversal control until the exit detection        cell 1AS2 is no longer obscured, and then for a pre-determined        period, and    -   control of the synchronization conveyor according to a movement        forwards with slight acceleration and a top speed of a        predetermined value V_(AV) until the exit detection cell 1AS2 is        obscured.

This method also increases the security of the baggage handling systemsby correcting the reliable monitoring of the said baggage.

An important characteristic of the method is that it does not usuallyrequire any additional material resources during the electromechanicaldesign of the injection lines.

Moreover, it is applicable to injections already in service in existinginstallations, which consequently allows for a clear reduction in theoperating costs of such installations.

The invention applies equally to known start/stop type injections, whereeach load pauses for synchronization with the sorting machine, ordynamic injections, where this pause only occurs if the trays that couldbe aimed for according to a continuous process are occupied.

The synchronization method according to the invention generallycomprises the following stages:

-   -   movement forwards control of the said conveyors and the        synchronization conveyor according to a first pre-determined        control law, until a second detection cell is obscured,    -   movement forwards control of the synchronization conveyor        according to a second pre-determined control law, until the exit        detection cell is obscured,    -   at the end of a pre-determined dwell time, test of the exit        detection cell.

This method is therefore characterized by the following stages:

-   -   if the test indicates that the said exit detection cell is still        obscured, operation of the injection device,    -   if the said exit detection cell is not obscured, reversal        control of the synchronization conveyor and the injection device        according to a third pre-determined control law, until the exit        detection cell is obscured,    -   continued reversal control of the synchronization conveyor        according to a fourth pre-determined control law until the exit        detection cell is no longer obscured,    -   stopping control of the synchronization conveyor 1AS for a        pre-determined period, and    -   movement forwards control of the synchronization conveyor        according to a fifth pre-determined control law, until the exit        detection cell is obscured.

The successive stages of the control of the synchronization conveyor andthe injection device according to either the first, second, third,fourth or fifth control law are advantageously repeated until the exitdetection cell test shows that the said exit detection cell is stillobscured after a pre-determined dwell time.

The synchronization method according to the invention is, for example,implemented by programming a synchronization control unit, in connectionwith the control of drive motors for the synchronization conveyor andthe injection device, the said synchronization control unit beingequipped to receive signals sent by the exit cells.

It can thus be implemented on a specific synchronization control unitadded to a pre-existing injection command/control equipment.

In this configuration, the control signals for the synchronizationconveyor and injection device drive motors generated by the pre-existingcontrol equipment are reproduced exactly at the terminals of thespecific control unit, and the specific control unit is provided with aloss of synchronization alarm signal generated by the pre-existingcommand/control equipment.

According to another aspect of the invention, a system is proposed tosynchronize loads before their injection onto a tilt tray type sortingmachine, for the implementation of the synchronization method accordingto any one of the previous claims, characterized in that it comprises:

-   -   first means to control the synchronization conveyor and the        injection device, when a load has overshot the exit detection        cell, according to a reversal with slight acceleration and a top        speed of a pre-determined value V_(AR), so that the load returns        to obscure the exit detection cell,    -   these first control means being designed to be activated until        the exit detection cell is no longer obscured, and for a        predetermined period, and    -   second means to control the conveyor according to a forward        movement with slight acceleration and a top speed of a        pre-determined value V_(AV) until the exit detection cell is        obscured.

The synchronization system according to the invention can be embodied inthe form of a specific control unit dedicated to synchronization,transparent to a pre-existing injection command/control unit. It mayalso comprise an additional detection cell to replace or supplement apre-existing exit detection cell.

The synchronization system according to the invention may be implementedon a dynamic injection site comprising at least one synchronizationconveyor with a load stop position and a synchronization sensor.

The description below gives other specific features and advantages ofthe invention. On the attached drawings, given as non-limitativeexamples,

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A describes the construction of a normal start/stop type injectionline, using motorized conveyors.

FIG. 1B illustrates the normal positioning of a load before injectiononto a sorting machine.

FIG. 1C illustrates the abnormal positioning of a sliding or rollingload on an injection line.

FIG. 1D illustrates the position of an injection line in a securitycheck circuit for a baggage handling system.

FIG. 2A shows, in a first embodiment of a synchronization systemaccording to the invention, a reversal sequence of the synchronizationconveyor and the injection device;

FIG. 2B shows, in this first embodiment, the continuation of thereversal sequence,

FIG. 2C shows, in this first embodiment, a subsequent forward movementsequence of the synchronization conveyor and the injection device, and

FIG. 3 shows a second embodiment of a synchronization system accordingto the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the implementation of the synchronization method according to theinvention, the drive motors of the synchronization conveyor 1AS andinjection device 1Al must have two directions of movement. The controlfor these motors must in practice be a speed variator, allowing forpre-determined control of the acceleration and drive speed.

When a load has overshot the exit detection cell 1AS2, the followingstages take place within the context of the synchronization methodaccording to the invention:

-   -   communicating to the synchronization conveyor 1AS and the        injection device 1Al a reversal (FIG. 2A) with slight        acceleration and a top speed of a predetermined value V_(AR), so        that the load returns to obscure the cell 1AS2 normally,    -   continuating this movement until the cell 1AS2 is no longer        obscured (FIG. 2B) and then continuation for a pre-determined        period: at this point, the injection device 1Al motor is        restored to its normal movement direction and setting,    -   communicating to the conveyor a forward movement (FIG. 2C) with        slight acceleration and a top speed of a predetermined value        V_(AV) until the cell 1AS2 is obscured.

The aim of the synchronization method according to the inventiondescribed above is thus to return the load to the normally plannedposition before the actual injection movement.

The speed setting values are chosen so that most loads that are unstableat a normal speed can be driven without sliding or rolling.

Because the synchronization method is automatic and the only loadexisting on the perimeter of the conveyors 1AS and 1Al can only be thatpreviously introduced from the spacer conveyor 1AQ2, the completeaccomplishment of the manoeuvre restores the monitoring of the load,i.e. the link between the identity of the load and its position isre-established.

The complete synchronization process, with correction to restore thepositioning and monitoring of the load in the event that it slides orrolls, is broken down into stages, the first four of which are known inthe prior art, namely:

-   -   1) according to a first pre-determined law, the conveyor 1AQ2        and the synchronization conveyor 1AS are controlled in forward        movement until the cell 1AS1 is obscured,    -   2) according to a second pre-determined law, the conveyor 1AS is        controlled in forward movement until the cell 1AS2 is obscured,    -   3) a predetermined dwell time is observed,    -   4) the cell 1AS2 is tested again,    -   5) if the cell is still obscured, the actual injection movement        is triggered, synchronized with the passing of an empty tray; if        it is not, an alarm is triggered to request human intervention.

Of course, each of stages (1) to (3) is accompanied by a dwell timelimit for the detection of other faults outside the scope of theinvention.

The synchronization method according to the invention consists inparticular of replacing stage (5) by stage (6) and the following stages:

-   -   6) if the cell is still obscured, the actual injection movement        is triggered; if it is not, according to a third predetermined        law the conveyors 1Al and 1AS are controlled in reverse until        the cell 1AS2 is obscured,    -   7) according to a fourth pre-determined law, the conveyor 1AS        continues in reverse until the cell 1AS2 is no longer obscured,    -   8) conveyor 1AS is stopped, and a predetermined dwell time is        observed (optionally zero),    -   9) according to a fifth pre-determined law, the conveyor 1AS is        controlled in a forward movement until the cell 1AS2 is        obscured,    -   10) stages (3) to (5) are carried out.

Each of the movement stages (6) to (9) is accompanied by a dwell timelimit for the detection of other faults outside the scope of theinvention.

Technically, the synchronization method according to the invention maybe embodied by the programming of a control unit such as an industrialcontroller of any known type, in connection with the control of themotors for the conveyors 1AS and 1Al and the cells 1AS1 and 1AS2.

According to a first embodiment of the invention, the method isadvantageously integrated into the injection from the design stage.

According to a second embodiment described in FIG. 3, thesynchronization method according to the invention is managed by aspecific piece of equipment that is added to a preexisting injection.This second embodiment is advantageously applicable to a sortinginstallation that is already in regular service, with no need to altereither the mechanics or the pre-existing command/control equipment.

The operation to implement the invention consists of:

-   -   replacing or modifying speed variators of the existing        synchronization conveyor 3S and of the existing injection device        3I to obtain two directions of movement and a range of speed        settings allowing for the method to be implemented.    -   exactly reproducing the control signals SC of the motors that        are known by the pre-existing command/control equipment, at the        terminals of the specific control unit 3C,    -   connecting the “loss of synchronization” alarm signal 3P        generated by the pre-existing command/control equipment to the        unit 3C,    -   optionally, installing an additional cell 3S3 if the position of        the pre-existing cell 3S2 is not suitable, and connecting either        3S3 or 3S2 in parallel to the unit 3C,    -   connecting an output from the specific control unit 3C to the        reset input 3R of the existing command/control equipment,    -   if necessary, connecting the specific control unit 3C to the        installation monitoring computer, via a data transmission link        3T.

In normal operation, the specific control unit 3C, which may be anindustrial controller, is completely neutral and “transparent” to theexisting command/control equipment.

When the existing command/control equipment emits the alarm signal 3P,it is known in advance that this command/control equipment has suspendedall movement, waiting for an intervention.

From this moment, the specific control unit 3C takes control of theconveyors 3S and 3I, to carry out the method according to stages (6) to(9) described above, using the preexisting cell 3S2 or the auxiliarycell 3S3 as a guide.

If the manoeuvre fails (due to the expiry of the guard timers), thespecific control unit 3C simply gives control of the motors to thepreexisting command/control equipment.

If the manoeuvre succeeds, the specific control unit 3C resets theexisting command/control equipment and then gives it control of themotors.

Any installation of this type is designed to return to normal operationafter an interruption such as a power failure. Therefore, when it hasbeen reset, the existing command/control equipment returns to a normalsituation and will complete the injection.

Generally, the existing command/control equipment will have sent a faultmessage to the monitoring computer. The data link 3T is provided to thisend, to send this same computer a specific fault cancellation message.

Of course, the invention is not limited to the examples described aboveand numerous adjustments can be made to these examples without leavingthe scope of the invention.

A person skilled in the art will easily understand that the inventionnaturally extends to dynamic injections, where there is at least onesynchronization conveyor with a load stop position and a specific sensoranalogous to the cells 1AS2 or 3S2 described above. A person skilled inthe art will also understand that it is easy, simply by using relays, tocreate specific control units that are totally transparent to existingcommand/control equipment to control the motors. In this case, the powerto the specific unit must simply be cut off to return fully to the prioroperation. This last point is important for intervention on systems Inregular service, on which only a few hours per day (for example, theclosure of an airport at night) are generally available to carry out themodification.

Thus, the synchronization method according to the invention may equallybe implemented on new systems and on systems in service, and provides inall cases a significant reduction in the injection failure rate andconsequently a rapid return on investment and/or improved performance ofthe sorting machines.

It is also important to note that in terms of airport security, theclear reduction in losses of monitoring and human intervention providesadditional quality in the so-called hold baggage control chain.

1. Method for synchronizing loads before their injection onto a tilttray type sorting machine, this machine comprising a set of trays (1AP)moving at a pre-determined speed in front of an injection systemcomprising conveyor means (1AQ1, 1AQ2) to advance the loads one by onetowards an injection site, a synchronization conveyor (1AS) to positiona load coming from the said conveyor means in a position allowing for itto be placed on a tray in ballistic mode, a device (1Al) for injecting aload coming from the said synchronization conveyor onto the sortingmachine, and means of detecting the position of the loads within theinjection system comprising a detection cell (1AS2) arrangedapproximately at the exit of the synchronization conveyor (1AS),characterized in that when a load has overshot the exit detection cell(1AS2), the following stages take place: control of the synchronizationconveyor (1AS) and the injection device 1Al according to a reversemovement with slight acceleration and a top speed of a pre-determinedvalue V_(AR), so that the load returns to obscure the exit detectioncell (1AS2), continuation of the reversal control unit the exitdetection cell (1AS2) is no longer obscured, and then for apre-determined period, and control of the synchronization conveyoraccording to a forward movement with slight acceleration and a top speedof a pre-determined value V_(AV) until the exit detection cell (1AS2) isobscured.
 2. Method according to claim 1, comprising the followingstages: control of the said conveyor means and the synchronizationconveyor (1AS) in a forward movement according to a first pre-determinedcontrol law, until a second detection cell (1AS1) is obscured, controlof the synchronization conveyor (1AS) in a forward movement according toa second pre-determined control law, until the exit detection cell(1AS2) is obscured, at the end of a pre-determined dwell time, testingof the exit detection cell (1AS2), characterized by the followingstages: if this test shows that the said exit detection cell (1AS2) isstill obscured, operation of the injection device (1Al), if the saidexit detection cell (1AS2) is not obscured, control of thesynchronization conveyor (1AS) and the injection device (1Al) in reversemode according to a third pre-determined control law, until the exitdetection cell (1AS2) is obscured, continuation of the reverse controlof the synchronization conveyor (1AS) according to a fourthpre-determined control law, until the exit detection cell (1AS2) is nolonger obscured, stop control of the synchronization conveyor (1AS) fora pre-determined period, and control of the synchronization conveyor(1AS) in forward mode according to a fifth pre-determined control law,until the exit detection cell is obscured.
 3. Synchronisation methodaccording to claim 2, characterized in that the successive controlstages of the synchronization conveyor and the injection deviceaccording successively to the first, second, third, fourth and fifthcontrol laws are repeated until the exit detection cell test shows thatthe said exit detection cell is still obscured at the end of apre-determined dwell time.
 4. Method according to claim 1, characterizedin that it is implemented by programming a synchronization control unit,in connection with the control of motors for driving the synchronizationconveyor (1AS) and the injection device (1Al), the said synchronizationcontrol unit being equipped to receive signals sent by the exitdetection cells (1AS1) and (1AS2).
 5. Method according to claim 1,characterized in that it is implemented in a specific synchronizationcontrol unit added to pre-existing injection command/control equipment.6. Method according to claim 5, characterized by the following stages:control signals (SC) for drive motors for the synchronization conveyorand injection device generated by the pre-existing command/controlequipment are reproduced exactly at the terminals of the specificcontrol unit (3C), and the specific control unit (3C) is provided with aloss of synchronization alarm signal (3P) generated by the pre-existingcommand and control equipment.
 7. System for synchronizing loads beforetheir injection onto a tilt tray type sorting machine, for theimplementation of the synchronization method according to claim 1,characterized in that it comprises: first means to control thesynchronization conveyor (1AS) and the injection device (1Al), when aload has overshot the cell (1AS2), in a reverse movement with slightacceleration and a top speed of a pre-determined value V_(AR), so thatthe load returns to obscure the cell (1AS2), these first control meansbeing designed to be activated until the cell (1AS2) is no longerobscured, and for a pre-determined period, and second means to controlthe conveyor in a forward movement with slight acceleration and to a topspeed of a pre-determined value V_(AV) until the cell is obscured(1AS2).
 8. System according to claim 7, characterized in that it isembodied in the form of a specific control unit dedicated tosynchronization.
 9. System according to claim 8, characterized in thatit also comprises an additional detection cell (3S3) to replace orsupplement a pre-existing exit detection cell (3S2).
 10. Systemaccording to claim 8, characterized in that the specific control unit(3C) is connected to a monitoring computer for the sorting installation,via a data link (3T), in particular to transmit a fault message and afault cancellation message.
 11. System according to claim 7,characterized in that it is implemented on a dynamic injection sitecomprising at least one synchronization conveyor with a load stopposition and a synchronization sensor.
 12. Application of thesynchronization method according to claim 1 to an existing baggagesorting system.